The basal ganglia and cerebellum are known to receive inputs from widespread regions of the cerebral cortex, such as the prefrontal, posterior parietal, and temporal lobes. According to one viewpoint, these inputs are integrated in the basal ganglia and cerebellum, and directed to the primary motor cortex, or other cortical motor areas, for use in the control of movement. However, Alexander, Delong, and Strick (1986) and Leiner, Leiner, and Dow (1991, 1993), proposed that significant portions of the output from the basal ganglia and cerebellum target the same regions of the frontal lobe which they receive input from. Thus, according to this scheme, it is possible that several non-motor "loops" exist between the prefrontal cortex and the basal ganglia and cerebellum. Despite the absence of direct anatomical evidence for the existence of such loops, there have been many suggestions about their role in a number of neurological and psychiatric disorders. The proposed experiments are designed to examine the possible existence of the prefrontal loops and the potential role of the basal ganglia and cerebellum in cognitive function. First, it will be determined if the basal ganglia and cerebellum have anatomical connections with regions of the prefrontal cortex that are known to be involved in cognitive function. Second, the degree of separation of these pathways from each other and from previously-described pathways that are involved in motor functions will be determined. To address these issues, retrograde transneuronal transport with the McIntyre-B strain of herpes simplex virus type 1 will be used in cebus monkeys. This technique will enable the direct observation of any pathways in the basal ganglia and cerebellum which are directed to the different prefrontal regions.